Four people were taken into custody Dec. 6 pending an investigation into a nightclub fire that killed at least 113 people in Russia's worst blaze in decades, investigators said.

An icon and candle are pictured at the site of the nightclub fire in Perm, Russia, on Dec. 6. AP PHOTO

About 120 remained hospitalized, many in critical condition, with injuries from the Dec. 5 blaze, which witnesses said was sparked by onstage fireworks that shot into the decorative twig ceiling of the Lame Horse club in the Ural Mountains industrial city of Perm.

The federal Investigative Committee said the suspects were the club's owner, the executive director, the artistic director and a businessman hired to install pyrotechnics on the night of the blaze.

Emergency Situations Minister Sergei Shoigu said that the club managers had been fined twice in the past for breaking fire safety regulations, which he did not specify.

Russian clubs and restaurants often cover ceilings with plastic insulation and a layer of willow twigs to create a rustic look, one of many uses of combustible materials in buildings by businessmen who bribe officials to look the other way.

Enforcement of fire safety standards is infamously poor in Russia, and there have been several catastrophic blazes at drug-treatment facilities, nursing homes, apartment buildings and nightclubs in recent years. The nation records up to 18,000 fire deaths a year.

The fire, first reported as an explosion, came at a time of increasing tension in the country after Chechen rebels claimed responsibility Dec. 2 for a bomb attack on a high-speed train traveling between Moscow and St. Petersburg that killed 26 people Nov. 27.